Heterojunction is an interface region formed by a contact of two different semiconductor materials. According to the conductivity types of different semiconductor materials, the heterojunction can be divided into homogeneous heterojunction (P-p junction or N-n junction) and heterotypic heterojunction (P-n or p-N). A heterostructure can be formed by multilayer heterojunctions. The heterostructure has excellent photoelectric properties, which can be applied to ultra-high-speed switching devices, solar cells and semiconductor lasers.
Since two-dimensional semiconductor materials have excellent electronic and optical properties, the two-dimensional semiconductor materials are researched more and more in recent years. However, the heterogeneous structures of conventional two-dimensional semiconductor materials are usually microstructures, applications of the two-dimensional semiconductor materials are limited.